Floors made from natural materials, such as wood and stone, continue to be an attractive option for many homeowners, building designers and architects. In many instances, homes and other buildings with wood- and stone- look floors command higher values than those with carpeting or vinyl flooring. Unfortunately, stone and solid wood floors are sensitive to scratching, difficult to maintain and relatively expensive and, as such, outside the means of many consumers. A demand for floors with the appearance of the higher cost natural materials, however, remains. In response to this demand, the flooring industry provides what are commonly known as laminate floors.
Traditional laminate floors are comprised of a surface laminate layer, a substrate, and a backer laminate layer. For example, the surface laminate layer may comprise a decorative sheet sandwiched between a structural layer and a protective layer. In turn, the surface laminate layer may then be bonded to a wood/resin composite substrate, such as particle board or fiberboard. The substrate is additionally bonded to a backing laminate layer that imparts balance and flatness to the total flooring composite. Because the decorative sheet in the surface laminate layer can be printed to almost identically mimic the appearance of natural wood and stone, the appearance of a solid wood or stone floor can be achieved at a cost more affordable to consumers and builders. Additionally, the surface laminate layer is much more resistant to scratching, and other abuse and thus is easier to maintain.
To form a high-pressure surface laminate, a thin overlay sheet impregnated with melamine resin and aluminum oxide grit to provide abrasion resistance, is layered on top of a decorative sheet. The decorative sheet is then layered on top of one or more kraft paper layers that have been impregnated with phenolic resin. The layered materials are then placed into a high-pressure press where they are cooked at approximately 300° F. under approximately 1000 psi for fifteen to sixty minutes. During the cooking process, the B-staged melamine and phenolic resins will flow and crosslink to bond these layers, thereby forming the surface laminate. Similarly, the high-pressure backer laminate is made by layering one or more kraft paper sheets that have been treated with phenolic and/or melamine resin and then cooking the materials in a high pressure press. Subsequently, the surface and backer laminates may then be adhesively bonded to the opposing sides of the wood/resin substrate, thereby forming a laminate panel that can then be machined into flooring.
In addition to laminate flooring made with high-pressure laminates, there is laminate flooring made with direct-pressure laminates. A direct-pressure surface laminate is made by either impregnating the decorative sheet with melamine resin containing aluminum oxide grit, or layering a melamine impregnated overlay sheet on top of a decorative sheet that may or may not be impregnated with melamine resin it self. These B-staged materials are laid directly onto a wood/resin substrate. Similarly, B-staged overlay and/or kraft paper sheets that have been treated with melamine and/or phenolic resin are layered on the opposing side of the wood/resin substrate. In contrast to the laminate flooring made with high-pressure laminates, the direct-pressure laminate components and the substrate are then pressed together at approximately 300° F. under 200-400 psi of pressure for one to ten minutes. The resulting panel can then be machined into direct-pressure laminate flooring.
A considerable portion of the total expense associated with the natural flooring products can be the costs associated with installation. Indeed, installation of hardwood, stone or laminate flooring can be a time consuming and laborious process. Procedurally, in the case of laminate flooring, each individual plank is properly positioned and subsequently secured to an adjacent piece. To secure the pieces against separation, an adhesive is typically applied to the abutting surfaces between each adjacent panel piece. The installer must use professional judgment in determining the amount of adhesive to apply. If too much adhesive is applied, then, upon assembly, any excess adhesive may be driven from the voids between the abutting surfaces and onto the decorative surface. This problem is generally referred to in the flooring industry as “squeeze out”. In many instances, the “squeeze out” adhesive is difficult to remove from the laminate surface and the installer often damages the laminate layer trying to do so. However, if too little adhesive is employed, then the bond between the panel pieces may lack adequate strength. For example, if the abutting surfaces of the adjacent pieces are not adequately coated with adhesive, this, in turn, may lead to unwanted separation and movement of the pieces throughout the lifetime of the floor.
Installers in the industry have employed a number of types of adhesives in assembling floors. Most commonly, installers have employed what are known as evaporative adhesives. Adhesives of this type are placed on the abutting surfaces of adjacent panel pieces in a wet or liquid state. Once applied, the coated surfaces are brought into intimate contact with one another. Over time, the solvent material evaporates leaving only the bonded solid or adhesive base, thereby binding the abutting surfaces of adjacent pieces. This type of adhesive, however, may be unwieldy to apply. As stated above, “squeeze out” can affect the laminate surface. Moreover, the curing time of evaporative adhesives may render the assembled floor unusable for 24 hours or more. Typically, when the evaporative adhesive employs water as a solvent, the water penetrates and swells the fiberboard core resulting in unsightly raised or “peaked” seams. One advantage, however, of the evaporative adhesive is that once the adhesive is fully cured or dried, it acts also as a sealant by coating the wood/resin composite core and repelling water from the seam between panels.
Another adhesive type may be a binary reaction or two-component adhesive. In employing a reaction adhesive, one of the abutment surfaces of a panel is generally pre-lined with a first compound and the opposite abutment surface of the adjacent panel is pre-lined with another compound. When separate, neither compound is an adherent nor presents tacky characteristics. However, when the two distinct compounds are brought into contact with one another, a chemical reaction occurs and the two distinct compounds form a single compound having tacky or adhesive properties. The requirement of two separate compounds and the fact that these compounds must be maintained separate prior to installation can add to the costs of manufacture as well as to the costs of storage.
The installer may also employ adhesives which require activation. In this case, the activation adhesive is typically in a dormant state (i.e. dry and non-tacky) when initially presented. However, the adhesive may be activated (i.e. rendered tacky) at a desired time. The adhesive may be activated in various ways, such as by rehydration, exposure to an ultraviolet light source, radio-frequency, or application of high pressure or heat. In any event, to use such systems the installer is required to perform the additional step of activating the adhesive before binding the two pieces. Moreover, the activation may require additional equipment, typically purchased at the expense of the installer.
Some manufactures have attempted to move away from the adhesive bonding modality all together. Essentially, these manufacturers fabricate panels having mechanical methods of securing adjacent floor panels. For example, two of the four sides of each panel are generally machined to form a groove running the length of a given side. The remaining two sides are machined to present tongues corresponding to, and designed to interlock with, the afore-mentioned grooves. However, the absence of an adhesive may render this “glueless” flooring system susceptible to moisture and water damage, and may permit some degree of separation of the panels. That is, if there is a separation between adjacent flooring panels, the lack of a protective adhesive provides an unrestricted moisture path into the wood/resin composite core. The ingress (and subsequent regress) of moisture into the wood/resin composite core may then cause floor panels to grow or shrink, respectively. Without an adhesive to seal the fiberboard core, the fiberboard would be more likely to dehydrate when in conditions of low humidity. As a result the flooring panel will shrink leading to a visually detectable and objectionable gap. Additionally, the moisture ingress can lead to swelling of the fiberboard core that is also visually objectionable to the customer.
To combat the moisture sensitivity of the glueless laminate flooring, many manufactures apply a sealant to the exposed edges of the panels during the manufacturing process. These sealants typically comprise a wax, oil or a coating, such as polyurethane. Unfortunately, these sealants do not improve the binding strength between the mechanically interlocked panels.
Accordingly, there exits a need for flooring systems that address many of the issues discussed above.